Daily COVID-19 Briefing: 4/20/20

Top news, reports and insights for today:

  1. Do stay-at-home orders work? Early adopting states with moderate-sized outbreaks show slower case growth
    Today, I am excited to show you a new graph I have been working on for more than a week. The graph below is my first attempt to make sense of a really important question: how does the rate of growth of new cases differ in states that adopted SAH orders early, vs. those that did so later, vs. those that still have not issued those orders. To address this, I looked at growth in daily new confirmed cases in states in the Western, Mid-western, and Southern regions. I’ll present results for Northeast states in a separate graph. In order to compare states with similarly scaled testing and epidemic intensity, I compare here only states with moderate-sized outbreaks, defined as more than 10,000 but less than 100,000 cases; so California, Michigan and some of the hardest hit states are not included. To compare apples to apples, I set day 1 for each state to be the date 100 cumulative cases was reported. Each state is therefore starting from the same place in it’s outbreak. The shape and steepness of these curves gives us clues about how fast the outbreak is occurring in each state.
    The thick black line represents the average growth across all 50 states. States above that line are seeing a faster growth in cases, while states below have a slower outbreak. The solid lines are states that enacted SAH orders before March 30. Dashed lines are states that adopted later (March 30 – April 7), and the dotted lines are states that still have not issued SAH orders. All the states above the national average (black line) were late adopters. The epidemic is moving fastest in Virginia (March 30), Missouri (April 6), North Carolina (March 30), Alabama (April 4), and Arizona (March 31). The flattest growth is seen in early SAH states: West Virginia, Oregon and Idaho. States that have not issued SAH orders are mixed. Arkansas has remained slow, while Nebraska and Iowa have been accelerating in recent days. The epidemic is growing roughly twice as fast in Utah and Oklahoma compared to early adopting states like Oregon, New Mexico and Minnesota. Wisconsin was above the US average until a week ago, but has slowed relatively since. This graph has limitations. It’s not based on a formal statistical model; it is purely a descriptive tool. Also, the rate of case growth, like everything else in this epidemic, is heavily influenced by differences in how well and how much each state is testing.
    What this means? Looking at states with moderate-sized outbreaks, early adoption of stay-at-home orders appears to be associated with slower epidemic progression. States like Oregon, West Virginia, Minnesota and Iowa stand out with slower rises in cases compared to the nation as a whole. States that adopted later stand out for substantially more accelerated case growth including Virginia, Missouri, North Carolina, Alabama and Arizona.
    This is my own work, the views expressed are my own, as are the faults and limitations. I welcome comments.
  1. U.S. deaths hold steady, new cases fall, Pennsylvania deaths spike?
    On Sunday, 1,634 new deaths (+5%) and 26,323 (+4%) new cases were reported in the U.S.. While the absolute numbers of deaths declined, the difference was less than the uncertainty of our count, so I am not inclined to conclude that deaths dropped significantly. The margin of decline in cases is encouraging and more likely to be significant. Pennsylvania, which has seen a modest 16% increase in cases over the last 3 days, reported 276 new deaths, far exceeding the previous daily high of 80 set on Saturday. According to a PA department of health press release yesterday, the spike in deaths occurred due to an announced change in reporting. As we are seeing in other states, PA is now reporting “electronic and probable-cause” deaths. Details are not provided, but this illustrates how state reporting systems are improving and adapting to changing circumstances. As the epidemic progresses, spikes will occur sporadically as states catch up in integrating the reporting of cases and deaths occurring outside hospital settings, including nursing homes, prisons, and at-home deaths.
    Noteworthy 3-day rises in deaths were reported in California (+31%), Minnesota (+42%), Alabama (+38%), North Carolina (+31%), Virginia (+33%), Massachussetts (+37%), Pennsylvania (+57%), and Rhode Island (+43%). Deaths are rising slowest in Idaho, Oklahoma, Arkansas, Georgia, South Carolina, Tennessee and Vermont.
  1. Should we expect another wave of COVID-19 in the Fall? Probably yes.
    One of the hottest questions right now is whether the novel coronavirus will resurge later this year after the initial wave dies down and the heat and humidity of summer slows the virus’s attack. I’m sure people are frustrated hearing this answer, but the truth is that we really don’t know for sure. The Guardian has a story today on this topic, which discusses some of the things we do and do not know. To address this, we need to do a little informal time traveling. First let’s look at countries that seem to have passed the first “wave”. Singapore is a country that received praise for its capacity to stamp out it’s initial outbreak, but recently new case clusters have broken out in “isolation units” used to house migrant workers. Blips of resurgence have been seen on the Johns Hopkins dashboard in other nations that had initial success including Germany, Japan, and Taiwan. Other post-peak countries remain largely quiet (e.g., South Korea). China has seen regional outbreaks in the North, but so far not a national-level second “wave”. A second form of useful time travel is to consider previous respiratory viruses, especially those that became pandemic. In 1918-19 “Spanish” influenza roared back in the Fall with a more lethal second wave, followed by a less lethal wave the following summer and fall. Multiple waves occurred in influenza pandemics in 1957 and 1968 and in the 2009 H1N1 pandemic, which also started in April, waned in the summer and resurged in the Fall.
    The bottom line: We don’t yet know if there will be a major resurgence of COVID-19 infections in the fall but there are good reasons to think it is possible and perhaps likely. 1) We are not likely to have a vaccine before the end of the year; 2) We have no reason to believe we are close to herd immunity; 3) other respiratory viruses have come in waves; 4) patience and tolerance for social distancing is waning now and will erode further as summer sets in. At very least, prudence suggests we need to assume a second wave may occur in Autumn; we should start preparing for that now. I will be surprised if it does not happen.
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